In recent years, electronic devices are highly required to be increased in integration in the electronic device production field represented by integrated circuit device production, and this allows a photolithographic technique for forming fine patterns to be required. Accordingly, photoresist compositions corresponding to photolithography using as exposure light, radial rays having a wavelength of 200 nm or less such as an ArF excimer laser (wavelength: 193 nm), an F2 excimer laser (wavelength: 157 nm) and the like are actively developed, and proposed are a large number of chemically amplified resist compositions comprising polymers having an acid-dissociable functional group and compounds (herein referred to as “a photoacid generator”) which generate acid by irradiation (herein referred to as “exposure”) of a radial ray. The above polymer having an acid-dissociable functional group comprises a basic structure in which a part of an alkali-readily soluble site of an alkali-soluble polymer is protected by a suitable acid-dissociable functional group, and selection of the above acid-dissociable functional group is very important in terms of controlling the performances of the photoresist composition.
Known as the existing acid-dissociable functional group are 1) groups having an adamantane structure (refer to a non-patent document 1 and a patent document 1) and 2) groups comprising a tetrahydropyranyl group (refer to a patent document 2). The acid-dissociable functional group is required to have both a high reactivity to acids and a stability in which it is not decomposed at a baking step, and is requested to have a heat stability of 130° C. or higher (refer to a non-patent document 3).
One of large problems of lithographic techniques in recent years includes line width variation of formed patterns which is called a line width roughness (herein referred to as “LWR”), and an allowable value thereof is required to be less than 8% of a line width (refer to a non-patent document 3). It is necessary for improving LWR to inhibit patterns from being deformed by swelling of a photoresist, that is, to allow a polymer which is a photoresist composition component to be less liable to be swollen.    Patent document 1: Japanese Patent Application Laid-Open No. 73173/1997    Patent document 2: Japanese Patent Application Laid-Open No. 88367/1993    Non-patent document 1: Journal of Photopolymer Science and Technology, Vol. 9, No. 3, p. 475 to 487 (1996)    Non-patent document 2: ITRS 2006, UP DATE version, part of lithography, p. 8    Non-patent document 3: ITRS 2006, UP DATE version, part of lithography, p. 7